I'm just not sure what to make of her as an actress. She makes a lot of questionable choices on this show, but it all seems to be in character, so I can't say it's ineffective. Whether she's any good or bad is almost beside the point, as long as she remains watchable.
With The Wire, I think I never got over the feeling that the story/characters were secondary to "The Point". I don't like when shows do that. Mad Men and Breaking Bad also had "Points" to make, but they never seemed like the main driving focus of those shows, so they didn't come at the expense of the characters/plot. Of course, those shows have their own problems, but they're within the realm of ordinary writing and editing. I can't say I have any problems with The Wire on a pure story level. But again, that's just not the main point of the show.